The present invention relates to a cover for a vehicle air bag, and more particularly to a cover which includes a displaceable flap portion of controlled flexibility incorporating one or more stiffness reducing elements which flap portion opens in substantially hinging fashion away from an internally disposed tear seam.
It is well known in motor vehicles to provide an air bag module for protecting a vehicle occupant. It is also generally known to provide an air bag module including an inflatable restraint cushion and an inflator for discharging gas to inflate the cushion upon sensing predetermined vehicle conditions. It is also known to provide air bag modules for the protection of a vehicle operator including cover elements overlying an inflatable restraint cushion in a stored position within the module. Such cover elements typically include tear seams at the interior which separate upon application of pressure by the inflatable restraint cushion during inflation such that the surface of the cover element folds outwardly in flap-like fashion generally away from the interior of the cover and towards the periphery thereof.
This invention provides advantages and alternatives over the prior art by providing a frangible cover for a vehicle air bag assembly which cover includes a displaceable flap portion of controlled flexibility for rotation in hinging fashion generally away from a tear seam at the interior of the cover and towards the perimeter of the cover to form an opening across the cover for egress of an underlying air bag cushion through the cover. One or more stiffness reducing members are arranged at the flap portion to control the internal stiffness of the flap portion and to facilitate ease of outward rotational displacement of the flap portion. Such stiffness reducing members may be arranged in a pattern extending in the region between the outer edge of the cover and a portion of an interior tear seam.
These advantages are accomplished in a potentially preferred form of the invention by providing a frangible cover of controlled stiffness for use in overlying relation to an inflatable air bag cushion. The cover includes a tear seam extending in a predefined pattern such as an xe2x80x9cHxe2x80x9d shaped pattern, xe2x80x9cUxe2x80x9d shaped pattern or xe2x80x9cIxe2x80x9d shaped pattern across the interior of the cover such that upon inflation of the air bag cushion the cover opens along the tear seam. A displaceable flap portion located in a region between the tear seam and the perimeter of the cover is folded back in a hinging manner in a direction generally away from the tear seam and towards the perimeter upon egress of the underlying air bag cushion. At least one stiffness reducing depression is disposed in predefined orientation across at least a portion of the displaceable flap portion between the tear seam and the perimeter of the cover to control the internal stiffness of the flap portion and to facilitate outward hinging rotation.
According to one aspect of the invention, the stiffness reducing depression is preferably of a generally elongate configuration having a length dimension greater than its width dimension. Such a depression of elongate configuration preferably extends in lengthwise fashion generally transverse to the direction of hinging movement of the flap portion so as to facilitate hinging rotation.
According to another aspect of the present invention, a number of stiffness reducing depressions of generally elongate configuration may extend in an arrangement across the flap portion between the tear seam and the perimeter of the cover generally transverse to the direction of hinging movement of the flap portion. The arrangement of the stiffness reducing depressions may be such that the stiffness of the flap portion either increases or decreases with increased distance away from the tear seam and towards the perimeter.